The present invention relates to a head maintenance mechanism for a serial type ink jet printer in which a carriage mounting thereon a print head is reciprocated in a widthwise direction of printing. More specifically, the invention relates to a head maintenance mechanism in which a single rotary drive source is used to drive a head cap, wiper and an ink suction pump.
With a serial type ink jet printer, a head maintenance mechanism is arranged in a position outside a region of printing performed by a print head, and wiping of dirt on a nozzle surface of the print head, capping intended for prevention of plugging of a nozzle orifice, and an operation of sucking ink in an increased viscosity from the nozzle orifice are performed by the head maintenance mechanism. To meet the needs of making a head maintenance mechanism for an ink jet printer small-sized, compact and inexpensive, related art head maintenance mechanisms are constituted by a configuration in which a single rotary drive source, such as stepping motors or the like, is used to cause movement of a wiper for wiping a nozzle surface, a capping action of a head cap for capping the nozzle surface, and an operation of sucking ink from a nozzle orifice as capped.
For example, Japanese Patent Publication No. 2000-141673A discloses a head maintenance mechanism of such configuration. With the head maintenance mechanism disclosed in this publication, rotation of a single motor in one direction causes a head cap and a wiper to be driven through a slide type rack and a cam mechanism, and reverse rotation of the motor causes a diaphragm suction pump to be driven through a cylindrical cam.
However, a head maintenance mechanism of a type in which rotation of a single motor in one direction causes a head cap and a wiper to be driven, and reverse rotation of the motor causes a suction pump to be driven, involves the following problems.
First, a cylindrical cam is generally used to convert rotary movements of a motor into reciprocal movements. Since such a cylindrical cam is continuously rotationally driven in one direction, there is a need of providing a position detector for detecting a reference or initial position of the cylindrical cam in order to control respective motions of the cylindrical cam.
Also, there is a need of separately providing a power transmitting mechanism for driving of a head cap and a wiper and a power transmitting mechanism for driving of an ink suction pump, which is disadvantageous in making a head maintenance mechanism small-sized and compact.
Further, a pump, for example, a tube pump needed to rotate forward and rearward cannot be adopted as an ink suction pump. More specifically, in the case where a tube pump is used, a roller rotates flattening an ink tube to perform an ink sucking action when a pump gear being a drive force input element of the pump is rotated forward, and the roller is put in a release state, in which the ink tube is not flattened, when the pump gear is rotated rearward. Since the release state is necessary after the ink sucking action, a tube pump cannot be used in the case of rotary driving in one direction.
Also, a head maintenance mechanism for an ink jet printer involves as an ink sucking configuration from a head cap with an ink sucking action, the case where ink is sucked from a nozzle orifice and the case where ink accumulated in the head cap is sucked (idle suction) in a state in which the head cap made in capping is put in an atmospheric opening state. In order to realize both of these ink sucking configurations, it is necessary to provide a mechanism for opening and closing a vent valve mounted on a head cap after there is established a state in which the head cap caps the nozzle surface. When such mechanism can be made compact, it is advantageous in making a head maintenance mechanism small-sized, compact or thin.
An object of the invention is to propose a head maintenance mechanism for an ink jet printer which is capable of controlling motions of a head cap, wiper and an ink suction pump without the use of any position detector.
Also, an object of the invention is to propose a head maintenance mechanism for an ink jet printer which is capable of driving an ink suction pump forward and rearward.
Further, an object of the invention is to propose a head maintenance mechanism for an ink jet printer in which a power transmitting mechanism for driving a head cap, wiper and an ink suction pump can be made compact.
Further still, an object of the invention is to propose a head maintenance mechanism for an ink jet printer in which a mechanism for switching an interior of a head cap capping a nozzle surface between opening to the atmosphere and not opening is made compact.
In order to achieve the above objects, according to the present invention, there is provided a maintenance mechanism for a print head having a nozzle surface in which are formed a plurality of nozzles, comprising:
a head cap, reciprocally movable between a capping position for covering the nozzles and a retracted position separated from the nozzle surface;
a pump, connected to the head cap;
a drive source;
a pump gear, rotated by the drive source to drive the pump;
a cylindrical cam, reciprocally rotatable between a first position and a second position to reciprocally move the head cap; and
a frictional clutch, which rotates the cylindrical cam together with the pump gear, but rotates only the pump gear when the cylindrical cam reaches each one of the first position and the second position.
Preferably, a cam groove is formed on an outer peripheral surface of the cylindrical cam in a predetermined circumferential angular range. The maintenance mechanism further comprises a cap driving pin slidably movable along the cam groove to reciprocally move the head cap.
Here, it is preferable that the maintenance mechanism further comprises an urging member which urges the cap driving pin toward a bottom surface of the cam groove.
Preferably, a first engagement member and a second engagement member are provided with the cylindrical cam, and a third engagement member is disposed at a predetermined position. A rotation of the cylindrical cam in a first direction is stopped when the first engagement member engages with the third engagement member, and a rotation of the cylindrical cam in a second direction is stopped when the second engagement member engages with the third engagement member.
Alternatively, it is preferable that a rotation of the cylindrical cam in a first direction is stopped when the cap driving pin reaches at a first dead end of the cam groove, and a rotation of the cylindrical cam in a second direction is stopped when the cap driving pin reaches at a second dead end of the cam groove.
Here, it is preferable that the pump gear and the cylindrical cam are coaxially arranged, so that they can be arranged in a compact manner.
Still here, it is preferable that the frictional clutch includes an urging member which presses one circular end surface of the pump gear and one circular end surface of the cylindrical cam together.
Further, it is preferable that the pump is a tube pump which performs a sucking operation only when the cylindrical cam is rotated in either one of the first direction and the second direction.
Here, it is preferable that the pump is arranged coaxially with the cylindrical cam.
Preferably, the head cap includes:
a cap body having an opening which faces the nozzle surface;
a cap holder, which holds the cap body;
an urging member, disposed in the cap holder to urge the cap body in a direction that the cap body is projected from the cap holder; and
a vent valve, closed when the cap body of the head cap placed at the capping position is pushed toward the cap holder by a predetermined amount against an urging force of the urging member, so that an interior space of the head cap is isolated from atmosphere.
Here, it is preferable that the cam groove includes:
a first portion which moves the cap driving pin so as to place the cap holder at a first capping position where the cap body covers the nozzles and the vent valve is closed; and
a second portion which moves the cap driving pin so as to place the cap holder at a second capping position where the cap body covers the nozzles and the vent valve is opened.
Still here, it is preferable that the cam groove includes a guide portion which guides the cap driving pin situated in the first portion to the second portion. The cap driving pin situated in the vicinity of one end of the first portion is guided to the second portion via the guide portion, when the cap driving pin is moved away from the one end of the first portion.
Still here, it is preferable that: the first portion includes a depth-decreasing portion in which a depth thereof gradually decreases toward the one end thereof; and the guide portion connects a part in the first portion in the vicinity of the depth-decreasing portion and the second portion.
Preferably, the cam groove is one continuous groove, and the predetermined circumferential angular range is 360 degrees or less.
Preferably, the maintenance mechanism further comprises an intermittent gear arranged coaxially with the cylindrical cam, so as to rotate integrally with the cylindrical cam. A driving force of the driving source is transmitted to the intermittent gear only in a predetermined circumferential angular range of the cylindrical cam between the first position and the second position.
Preferably, the maintenance mechanism further comprises:
a wiper, reciprocally movable between a wiping position for wiping the nozzle surface and a standby position; and
a wiper driving pin, slidably moving along the cam groove to reciprocally move the wiper.
The cam groove includes:
a first dead end portion, at which the wiper driving pin is placed when a rotation of the cylindrical cam in a first direction is stopped;
a wiper driving portion, continued from the first dead end portion, which moves the wiper driving pin to reciprocally move the wiper;
a second dead end portion, at which the cap driving pin is placed when a rotation of the cylindrical cam in a second direction is stopped; and
a cap driving portion, continued from the second dead end portion, which moves the cap driving pin to reciprocally move the head cap.
Here, it is preferable that the maintenance mechanism further comprises an intermittent gear arranged coaxially with the cylindrical cam, so as to rotate integrally with the cylindrical cam. A driving force of the drive source is transmitted to the intermittent gear only in a predetermined circumferential angular range of the cylindrical cam between the first dead end portion and the second dead end portion of the cam groove.
Here, it is preferable that the pump is a tube pump which performs a sucking operation only when the cylindrical cam is rotated in the second direction.
In the above configurations, the torque of a single drive source is transmitted to the cylindrical cam through the frictional clutch from the pump gear, and a finite rotation of the cylindrical cam causes at least one of the head cap and the wiper to move. Accordingly, it is possible to place the cylindrical cam of the finite rotation type in an initial or reference position without the use of a position detector for detecting the rotation angle of the cylindrical cam. Therefore, an inexpensive head maintenance mechanism easy to control can be realized.
Since there is no need of separately arranging the power transmitting mechanisms for the suction pump, the head cap and the wiper, it is possible to realize a small-sized and compact head maintenance mechanism.
Since forward and rearward rotations from the drive source can be transmitted to the suction pump, it is possible to switchingly control a state of a pump, such as a tube pump, by switching of a direction of rotation of the drive source.
Since the cam groove is formed so as to establish a state in which the head cap seals the nozzle surface, and a state in which the head cap seals the nozzle surface but the interior space of the head cap is communicated to atmosphere, there is no need of separately providing a drive mechanism for driving a valve mechanism for opening of the head cap to the atmosphere and it is possible to realize a small-sized and compact head maintenance mechanism.
Since the cylindrical cam, the pump gear and the suction pump are arranged in a coaxial manner, a predetermined space in a direction perpendicular to the coaxes can be saved so that a small-sized and compact head maintenance mechanism can be realized.